S2-浓度对含盐污水中10#碳钢腐蚀性能的影响

 目前中国的炼油厂换热器多采用碳钢材质，换热器是石化设备中失效最快、损失最严重的设备之一，尤其是水相换热器的腐蚀更为严重。水相介质中通常含有一定量的S^2-、Cl^-、Ca²⁺和Mg²⁺，关于碳钢在含硫介质中的腐蚀行为，国内多数研究方向是应力情况下硫化物引起的应力腐蚀开裂问题，无应力状态下碳钢在含硫介质中的腐蚀行为研究得比较少。本文针对兰州石化某常减压装置换热器管束（主要材质10^#碳钢）在使用过程中的腐蚀问题，采用高温高压釜实验和电化学测试方法，研究壳程介质中S^2-浓度对10^#碳钢在含盐污水中腐蚀行为的影响，利用宏观照片和X 射线衍射仪XRD 表征腐蚀产物的形貌和相结构组成。实验结果表明，在测试区间内，随着腐蚀介质中S^2-含量的增加，试样表面生成的FeS 使得碳钢的均匀腐蚀速率逐渐降低，当介质中S^2-含量升高到250 mg/L 时，碳钢换热器管束的腐蚀程度由严重腐蚀转变为中度腐蚀，XRD 分析结果显示腐蚀产物为Fe₃O₄、CaCO₃和FeS；同时，当腐蚀介质中S^2-含量小于100 mg/L 时，由于介质中侵蚀性Cl^-存在，溶液中的Cl^-更容易穿过疏松的腐蚀产物膜层到达膜与基体界面处腐蚀基体，使得碳钢表面出现明显的点蚀现象，且介质中S^2-含量越低，试样抗点蚀性能越差。

Influence of S2-Concentration on the Corrosion Resistance of 10# Carbon Steel in Saline Wastewater

The corrosion of a refinery heat exchanger, especially a water-phase heat exchanger, is a serious issue. The corrosion perforation and scaling of tubes are the main causes for the heat exchanger failure due to the existence of plenty of S^2-, Cl^-, Ca²⁺ and Mg²⁺ in the corrosion medium. Based on the experience of corrosion of refinery heat exchanger tubes (10^# carbon steel) in their operation processes, the corrosion behaviors of 10^# carbon steel in saline wastewater with different S^2-concentrations are investigated by means of the immersion test and the electrochemical methods. The surface photographs and the compositions of corrosion products are taken and determined by digital camera and X-ray diffraction spectrometer. The experiment results indicate that the uniform corrosion rates of 10^# steel decrease gradually with the increase of the S^2-concentration in the corrosion medium within the scope of the test. The corrosion degree of 10^# carbon steel comes down to a moderate corrosion from a heavy corrosion when the S^2-concentration in the medium is higher than 250 mg/L. XRD results show that the main compositions of the corrosion products are Fe₃O₄, CaCO₃ and FeS. Meanwhile, Cl^- in the corrosion medium can penetrate the corrosion product to accumulate and produce the pit corrosion on the surface of 10^# carbon steel because of the existence of Cl^-when the S^2-concentration in the medium was less than 100 mg/L. And the pitting corrosion resistance becomes worse with the decrease of the S^2-concentration.